RISK OF BREAST CANCER LOCAL RECURRENCE

BOSTON — The risk for local recurrence of breast cancer decreases as event-free survival lengthens, according to an analysis of a large database from the Netherlands.

The study, which also demonstrated that recurrence risk varies substantially by subtype, should help physicians counsel women with breast cancer.

"The risk of local recurrence as a first event within 5 years after diagnosis was low overall, at 3%. It differed by subtype, with ER-positive, PR-positive, HER2-negative breast cancer with the lowest risk and triple-negative with the highest risk," said Martine Moossdorff, MD, who is currently a doctoral candidate at Maastricht University Medical Center, in the Netherlands.

Dr Moossdorff presented the study here at the Society of Surgical Oncology (SSO) 2016 Cancer Symposium.

"The risk of local recurrence decreased with event-free time. Overall, it was 1% after 3 event-free years," she said.

The prognosis of patients after treatment for breast cancer is often expressed as a 5-year or 10-year probability of event-free survival. Various studies have shown that the 5-year local recurrence rate for breast cancer is around 3%, but is the rate affected if a patient visits a clinic 2 years after treatment and is found to have had no events?

"Is her chance of developing a local recurrence within 5 years still 3%, or has it decreased, because the event-free years are prognostic, and does it matter what kind of cancer she had?" asked Dr Moossdorff about such a clinical scenario.

To answer these questions, the researchers analyzed data from women diagnosed with breast cancer between 2005 and 2008 in the Netherlands Cancer Registry. This database includes all newly diagnosed breast cancer patients in the Netherlands. The primary endpoint was local recurrence as a first event.

Of the 34,453 patients in the analysis, more than half had estrogen receptor–positive (ER+), progesterone receptor–positive (PR+), HER2-negative (HER2-) breast cancer (51.6%).

Overall, the risk for recurrence at 5 years was 3.0%. The risk varied by subtype: ER+, PR+, HER2+, 2.2%; ER+, PR-, HER2-, 2.4%; ER+, HER2+, 2.8%; ER-, HER2+, 4.7%; and triple negative, 6.9%.

The investigators selected patients who were event free at 1, 2, 3, and 4 years after diagnosis, and then recalculated the risk for recurrence.

After 1 event-free year, the risk for recurrence dropped to 2.4%. After 2 event-free years, the risk dropped to 1.6%. Further decreases were seen 3 event-free years (1.0%) and after 4 event- free years (0.6%). The risk varied by subtype (see Table). "The decrease was observed in all subtypes, but the decrease was most pronounced in the first few years in subtypes with the highest baseline risk, those who were ER-/HER2+ and those who were triple negative," reported Dr Moossdorff.

Table. Local Breast Cancer Recurrence Rate Varies by Subtype

	At Diagnosis, %	After 1 Event-Free Year, %	After 2 Event-Free Years, %	After 3 Event-Free Years, %	After 4 Event-Free Years %
ER+, PR+, HER2-	2.2	2.0	1.5	1.0	0.6
ER+, PR-, HER2-	2.4	2.0	1.4	0.9	0.5
ER+, HER2+	2.8	2.2	1.5	1.0	0.4
ER-, HER2+	4.7	3.4	2.0	0.7	0.2
Triple negative	6.8	4.6	2.7	1.6	1.1

Dr Moossdorff said that the data can be used to counsel individuals who are anxious at follow-up visits and that the low rates call into question the use of follow-up after a few event-free years.

"This is outstanding work and a beautiful use of a big dataset," said Jeffrey Drebin, MD, PhD, chairman of the Department of Surgery at the Perelman School of Medicine of the University of Pennsylvania, in Philadelphia, who was not involved with the study. "I think it is something we can use to reassure our patients."

Dr Drebin pointed out that even more than being concerned about recurrence, patients with breast cancer are worried about metastatic disease and death, so future research efforts should also include these outcomes.

Dr Moossdorff and Dr Drebin have disclosed no relevant financial relationships.

Society of Surgical Oncology (SSO) 2016 Cancer Symposium: Abstract 4. Presented March 4, 2016.